Few modern religious Christian scholars approach the clarity and depth of writing as Richard John Neuhaus, Canadian Catholic priest and writer.  One of his recent articles in the always excellent First Things has a salient couple of paragraphs on the difference between Mormonism and Christianity.  (HT:  Evangelical Outpost)

Here’s what Neuhaus wrote:

I believe that many Mormons are Christians as broadly defined by
historic markers of Christian faith. That does not mean that the Church
of Jesus Christ of Latter-day Saints is Christian. It is indisputably
derived from Christianity and variations on Christianity, but its
distinctive and constituting doctrines are irreconcilable with even a
very liberal construal of biblical Christianity. It is, as Rodney Stark
and many others have argued, a new religion and, by the lights of
historic Christianity, a false religion. It is true that there are
Mormon scholars who are working mightily to reconcile the LDS with
Christianity, and one wishes them well, but they have their work cut
out for them.

It is not an unreasonable prejudice for people who, unlike Alan
Wolfe et al., care about true religion to take their concern about
Mormonism into account in considering the candidacy of Mr. Romney. The
question is not whether, as president, Mr. Romney would take orders
from Salt Lake City. I doubt whether many people think he would. The
questions are: Would a Mormon as president of the United States give
greater credibility and prestige to Mormonism? The answer is almost
certainly yes. Would it therefore help advance the missionary goals of
what many view as a false religion? The answer is almost certainly yes.
Is it legitimate for those Americans to take these questions into
account in voting for a presidential nominee or candidate? The answer
is certainly yes.